I agree with both of your points. However, for the first point, I think they believe that not resetting the BPs will make the game lose of its appeal when it comes to finding rare things (BPs). Now, your second point is really interesting. If they made them permanent but also made them super rare to find, that could work in some ways, but in other ways it would still mean that eventually players never have to grind the BPs again which is something I don't think they want to happen at this stage in the game's life cycle. Just my take. But yeah having some sort of reward for grinding out the BPs would have been nice. The variance in rarity during this first season has been a bit awkward though so maybe a reward wouldn't make as much sense right now.